NRF24L01 radio not connecting

Hello, please help me since I'm stuck!
My sensor node has problem with the radio communication. I am using an NRF24L01.
Actually I do not think that the radio, nor the Arduino is faulty. I have tested both on an Easy/Newbie PCB and they are working good.
I have designed my own PCB (https://www.openhardware.io/view/374/MyQTherm-replace-IQTherm-heating-thermostat). The radio does not communicate with my gateway when I use this PCB.
The strange thing is that if I touch the radio chip with a finger the signals get through! Or even if I let the chip lie on a plastic surface it works. I also tested to fix a short cable with tape onto the chip and it works. When I remove my finger, cable or move the chip from a surface, the communication is interupted.
As I said above, I have tested the radio chip and the Arduino (Pro Mini 5V clone) in another setup so I know they are good.
In my investigations I tried with a fresh PCB (MyQTherm) an soldered just the NRF24L01, Arduino, LE33 voltage regulator and 4.7 uF capacitor for the radio. Leaving out all other stuff. Then I connected the Arduino to a serial chip connected to USB. So the node was then powered from USB. In this test the radio was also behaving faulty as described above.
I have tested 3 of my own designed PCBs with the same result.
Any ideas?

@kontrollable if I'm understanding the PCB design correctly, the nrf24l01 module will be placed so the nrf's antenna is in the middle of the PCB. Is that correct? If so, I'm pretty sure we have an answer: there is a lot of metal close to the antenna, which will interfere with the radio signal.

OK, so enabled MY_DEBUG on my serial gateway. MY_DEBUG was already enabled in my sensor node.
I found that the gateway did not receive any signals from the node at all.
The node reports that it does not find any parent.
So my conclusion is that the radio on the node sends a weak signal.